Process for preparing polymers of conjugated dienes

ABSTRACT

CONJUGATED DIENES ARE POLYMERIZED WITH AN ORGANOALKALIMETAL POLYMERIZATION INITIATOR WHEREIN THE PROPERTIES OF THE CONJUGATED IENE POLYMERS ARE IMPROVED BY THE ADDITION OF AN ALLYL AMINE THERETO SUCH AS TRIALLYLAMINE, PRIOR TO DEACTIVATING THE POLYMERIZATION INITIATOR.

United States Patent 3,658,776 Patented Apr. 25, 1972 ABSTRACT or THEVDISCLOSURYE Conjugated dienes are polymerized with an organoalkalimetal polymerization initiator wherein the properties of the conjugated diene polymers are improved by the addition of an allyl amine thereto such as triallylamine, prior to deactivating the polymerization initiator.

This invention relates to a process for improving the properties of a conjugated diene polymer. This invention relates to a process for providing a conjugated diene polymer having 'a broadened molecular weight distribution and exhibiting reduced cold flow properties.

A process has now been discovered for improving the processing characteristics of conjugated diene :homopolymers and copolymers, in either random or blockform, without deleteriously affecting the physical properties of the polymers.

According to my discovery, conjugated ,dienes are polymerized with organoalkali-metal initiators wherein allyl compounds of nitrogen are admixed to the polymerization reaction mixture prior to deactivation of the polymerization initiator to provide a polymer with improved processing characteristics. e

It is an object of this invention to provide a conjugated diene polymer exhibiting improved processing properties. It is a further object of this invention to provideaprocess for broadening the molecular weight distribution and reducing the cold flow of conjugated diene polymers:

Further objects and advantages of this invention will become apparent to those skilled in the art from; the following description and discussion herein set forth.

In accordance with my invention, the allyl compound is admixed to the polymerization reaction mixture under conventional polymerization conditions at any time prior to deactivation of the organoalkali-metal initiator employ- 1 ed to initiate the polymerization of the monomers. The allyl compounds can thus be added to the polymerization reaction mixture at the commencement ,of the polymerization process, such as following the charge of monomer materials, vulcanization accelerators, plasticizers, and the like, to produce articles such as tires, belting, shoe soles, wire coatings, and the like.

Homopolymers and copolymers of conjugated dienes or copolymers of conjugated dienes with monovinyl-substituted aromatic compounds can be employed according to this invention.

Conjugated dienes suitable for use in this invention contain from about 4 to 12 carbon atoms per molecule. Exemplary conjugated diene monomers include 1,3-butadiene; isoprene; 2,3-dimethyl-1,3-butadiene; 1,3-pentadiene; 3- methyl-l,3-pentadiene; 1,3-heptadiene; 3-butyl-1,3-octadiene; 2-phenyl-1,3-butadiene; and the like. Mixtures of the above conjugated diene monomers can also be employed in this invention.

Monovinyl-substituted aromatic monomers suitable for I use in this invention incopolymerizing with the abovestated conjugated dienes are those compounds containing from about 8 to 20 carbon atoms per molecule. Suitable monovinyl-substituted aromatic monomers include styrene; l-vinylnaphthalene; 2-vinylnaphthalene; 3-methylstyrene; 3,5-diethylstyreneg 4-dodecylstyrene; 4-cyclohexylstyrene; 4-phenylstyrene; 4-dimethylaminostyrene; 4- methoxystyrene; 4-methoxy-l-vinylnaphthalene; and the like. Mixtures of the above monovinyl-substituted aromatic monomers can be employed. When monovinyl-subtogeneous pressures. It is usually desirable to operate at and initiator, or can be added during the polymerization reaction, or after the polymerization is essentially complete. In the latter instance, wherein essentially all of the monomer(s) have been converted to polymers a period of time generally from about 0.1 to 6 hours and preferably 0.5 to 2 hours is provided for the reaction of the allyl compound with the polymerized monomers prior to deactivation of the organoalkali-metal initiator. It is preferred to add the allyl compounds of this invention to the polymerization reaction mixture at the commencement of the polymerization.

The amount of allyl compound employed in this invention is in the range from about 0.1 to 5, preferably 0.25 to 1, millimoles of allyl compound per 100 grams'of monomers employed in preparing conjugated diene homopolymers or copolymers. j

The polymers produced according to this invention can be processed easily, have a reduced tendency to cold flow, have -a broadened molecular weight distribution, and a good balance of physical properties. The polymers can be compounded and vulcanized with the usual reinforcing pressures sufiicient to maintain the monomeric material essentially in the liquid phase. The pressures will thus depend upon the particular materials being polymerized, the solvent being employed, and the temperature at which the polymerization is carried out. However, higher pressures can be employed, if desired, these pressures being obtained by some such suitable method as the pressurization of the reactor with a gas which is inert with respect to the polymerization reaction.

1 The polymerization can be carried out generally at a temperature within a range of about 30 to 150 C., preferaby from about 50 to 100 C. The time that is employed will likewise depend upon several factors such as choice of monomers, initiators, temperatures, allyl compounds, and the like. Generally from about 0.01 to 100 hours, preferably from about 1 to 20 hours, are employed for .the polymerization and the preparation of the im-' proved polymer according to this invention.

The polymerization can be carried out in the presence 7 or absence of a solvent mixture. The polymerization is preferably carried out in the presence of a solvent mixture comprising a hydrocarbon selected from aromatic hydrocarbons, paraflins, cycloparafiins, and the like. The hydrocarbon diluent employed can vary widely, but preferably contains from about 3 to 12 carbon atoms per molecule.

' Mixtures of two or more hydrocarbon diluents can be l r n t t vst- .Ama i s s hsrq am s such as between'0.005 to 50 weight percent of the'total solvent mixture, can be employed to promote the formation of random copolymers. Polar materials such as ethefs, thioether's and" tertiary amines can'be suitably employed. Exemplary are dimethyl ether, diethyl ether, ethylrnethyl ether, ethylpropyl ether, di-mprop'yl'ether, di-n-octyl ether, dibenzyl ether, diphenyl 'ether, anisole, tetramethylene oxide, 1,2-dimethyloxyethane, 1,3-dioxanedimethyl sul- -fide, 'pziraldehyd,diethyl sulfide, 'di-n-propyl sulfide, din-b'utyl sulfide, --methyl"e'thyl sulfide, dimethylethylamine', tri-n-propylamine," tri-n-butylamine, trimethylamine, triethylamin'e, N,N-dimethylaniline, pyridine, quin'oline, N= ethyl piperidine, N-methyl-N-ethylaniline,N-methyl morpholirie, and the like. w v I The use of polar solvents as randomizing; agents is fully disclosed in US. Pat. 2,975,160 issued to Zelinski Mar. 14, 1961, and is hereinincorporated by reference thereto.

Randomizing agents such as potassium alkoxides or hexamethylphosphoramide can also be employed.

At the completion of the polymerization'reaction and subsequent to the treatment with the allyl compound according to this invention the-'r'eaction n'iixtur'e'c'an be treated according to conventional methods to inactivate the catalysts or to recover the-polymer product. Any suitable treating method can be used and one method for accomplishing the desired treatment comprises "adding to the reaction mixture a catalyst inactivating material such as water, alcohol, e.g., ethyl alcohol or; isbpro'pyl alcohol, an organic or inorganic acid or the like. Various compounds suitable as antioxidants, such'as' substituted phenols, can be added to the polymer solution prior' 'to the precipitation of the polymer. The precipitated polymer can be recovered by filtration, decantation, or the like, when subjected to further purification separation processes. 11 l According to this invention any conventional brganoalkali-metal initiator that can polymerize the monomeric materials hereinbefore described can be employed. Organoalkali-metal initiators represented by theformula R(M)x wherein M is an alkali metal, R is a hydrocarbon radical selected .from the group consistingofaliphatic, cycloaliphatic, and aromatic radicals containing'from about 1 to 20 carbon atoms, and x is an' integer from 1 to 4, areknown to be excellent organoalkali-metal polymierization initiators that can be preferably employed. Hydrocarbyllithium polymerization initiators are preferred; Exemplary of the aforegoing initiators are methyllithium; isopropyllithium; n-butyllithium; tertiary-octyllithium; sec-butyllithium; phenyllithium; naphthyllithium; v4-butyl? phenyllithium; 1,4-dilithiobutane; 1,5-dilithionaphthalene; 1,5,10,20 tetralithioeicosane; 1,2,4,6 tetralithiocyclohexane; 4 butylphenylsodium; 4 phenylbutylcesium; 4- cyclohexylbutylpotassium; and the like. The. amount of initiator employed'is generally in the range tofprovide from about 0.1 to 100, preferably 0.5 to 10, riiilliequivalents of alkali metal per 100 grams of monomers.

'As herein stated any alkali-metal based initiatorsgsuitable for the polymerization of the hereinb'efore described monomeric materials can be employed according to this invention. I g

Multifunctional polymerization initiators" such as' pre5 pared from the reaction between organo'r'nonblithium' compounds with polyvinyl phosphine compounds or pol'y vinyl silane compounds such as disclosed in US. patent application Ser. No. 795,364, filed Jam-30, 1969,: b'y Ralph C, Farrar can be suitably employed: Other novel multifunctional initiators such as-disclosed inU:S.. patent' R' N(CH CH=CH wherein R is a hydrocarbon 4 radicalselected from the group consisting 'of aliphatic, cycloaliphatic,,and aromatic radicals containing 'froml to 20 carbon atoms, and m is 1,2 or 3 and nis the valence of N'minus m. v

Allyl compounds that can be employed according'to this invention can be represented by the following 'examples': tria'llylamine, eicosyldiallylamine, 'diethylallylamine, 'cyclohexyldiallylarnine, diphenylallylamine; and thelike'. I Illustrative of the "foregoing-discussion and not to be interpreted as a limitation on the" scopethereof or on the ingredients therein employed the following examples are p e x q Polybutadiene was. prepared according to ing polymerization recipe:

- Polymerization recipe the $0110....

Parts, by wt. 1,3-butadiene a Mhm.:Gram millimoles per 100 grams -ofxiionomer. In these runs jcyclohexane was charged 'tQ.;the -.react or followed by a nitrogen purge. after whichibutadiene was addedn-Butyllithium was added next, followed by, tl 1e triallylarnine in Run 1. Temperature was adjusted .to the indicatedlevel and each mixture wasagitatedfihroughv out the polymerizatiomAt the end of the polymerization reaction a 10 weight percent solution of 2,2 -methylene- 'bis (4-methyl 6 tert-butylphenol)antioxidant in a 50/50 percent by volume isopropylalcohol/toluene,was added with the amount being sufiicientto provideabout 1 part by. weight of the antioxidant per .100 parts of thepoly: mer. Each mixture;was coagulatedbystining with isopropyl alcohol andthepolymerseparatedand dried. The results arerepgrted-inr'lablql and demonstrate that the triallyla'mine-ad dition provides a ,broadeningof the mo; lecular weight distribution (higher H.I.) while the micro, structure is essentially unchanged Use of the allyl com pound fthis invention t hus provides a polymer of inrproved, processing pharacteristics accompanied with good phys P pe t "I TABLE I f t Unsaturation x 'i w 'Conv'ef-TInherent 1 Rum. A ,(TAA) sion, .viscos- Trans.v Vinyl, I No." mhm. percent ity percent pereeut a Temperature, C .70 m h first followed by a nitrogen purge. Butadienerandl styrene were added next to form a monomer mixture, then tetrahydrofuran followed by the n-butyllithium. Triallylamine, if employed, was added next or as indicated in Runs 2 and 5. The temperature was adjusted to the indicated level and each mixture was agitated throughout the reaction period. Polymers were recovered from each run in the same fashion as reported in Example I.

The results reported in Table II demonstrate that according to this invention the addition of a triallylamine produces a broadening of the molecular weight distribution, a reduction in the cold flow, and an increase in the Mooney viscosity of the polymer. It is therein demonstrated that the triallylamine can be added initially, during the polymerization, or after the polymerization is complete but prior to shortstopping the reaction mixture.

TABLE II v ML-4 6 Cold -Inherent Run (TAA) (n-BuLi) at flow, viscos- N0. mhm. mhm. 212 F. mg./min. H.I. ity

EXAMPLE IH Additional'runs were made polymerizing l,3-butadiene with n-butyllithium initiator employing triallylamine according to the instant invention. The polymerization recipe was the same as that employed in Example I and the results from these runs are reported in Table III.

These results again demonstrate that the addition of the allyl compound initially, during, or after polymerization is essentially complete, produces a broadening in the molecular weight distribution, increase in the inherent viscosity and Mooney viscosity, and a decrease in cold flow in'the conjugated 'diene polymers made according to this invention. All of these caracteristics are demonstrative of polymers 'with improved processing characteristics.

- TABLE III ML-4 Cold x Inherent (TAA) at flow, viscosmhm. 212 F. rug/min H.I ity v 0. so 28.5 24.8 1. 29 2.11 0. 35 23. 18. 1. 24 1. 97 l 0.35 22 24.3 1. 1.93 18 37. 1 1. 19 1. 84

a 'TAA added after 2.2 hours reaction. v Conversion in each run was 100 percent. i As reported in Table II footnotes.

EXAMPLE IV TABLE IV (n-BuLi) (TAA) ML-4 at Gold flow Inherent mhm. mhm. 212 F. mgJmin. H.I.viscosity 1. 3 0. 43 33 2. 5 Not determined 1. 4 0. 47 27 5. 0 1. 78 1.38

1. 2 8. 0 Not determined 1. 3 26 8. 4 l. 27 l. 42

Conversion in each run was 100 percent. b As reported in Table II footnotes.

EXAMPLE V Additional runs were made in which 1,3-butadiene and styrene were copolymerized by using a multifunctional lithium' initiator formed as the reaction product of sec butyllithiu-m with triallylamine, Triallylamine was also employed according to this invention to improve the processing properties of the polymer thus prepared. The polymerization recipe, charging procedure, and polymer recovery method were the same as those employed in Example IV. The results of the runs are reported in Table V and demonstrate that by an addition of the allyl compound of this invention a decrease in cold flow and a polymer with improved processing properties is obtained.

Conversion in each run was 100 percent.

b Initiator prepared by reacting ml. 01:11.5 M secbutyllithium incyclohexane with 12.8 g. (20 millimoles) of 'triallylamine for 20 minutes at 70 C.

0 Based on sec-bwtyllithium. As reported in Table II footnotes.

EXAMPLE VI Butadiene/styrene random copolymers were prepared according to this invention and according to the following polymerization recipe:

I Polymerization recipe Parts by wt.

1,3-butadiene 75 Styrene v 25 Cyclohexaneh. 790 Initiator Variable Triallylamine (TAA) Variable Tetrahydrofuran 1.5 Temperature, C. '70 Time, hours Variable evaluated as shown by the results in Table VII. The results shown in Tables VI and VII demonstrate that butadiene/styrene copolymers prepared according to this invention show improvements in processing properties and physical properties When compared to'control polymers prepared without the use of allyl compounds of this invention. Y

TABLE VI Run Initiator (TAA) Time, ML- 4 mg] viscos- No. (mhm.) mhm. hours at 212 F. min. ity

l n-BuLi (1.1) 2.5 47 0.57 1.67 2 n-BuL1 (1.3) 0.4 2 46.5 0.0 1.68

B Conversion in each rim was 100 percent. As reported in Table II footnotes.

TABLE VII Compounding recipe Parts, by wt.

Polymer 100 IRB No. 2 1 50 Zinc oxide 3 Stearic acid '2 Flexamine 2 1 Philrich 5 3 l0 Sulfur 1.75 Santocure 4 1.2

Ikndustry Reference Black No. 2, a high abrasion furnace PROCESSING PROPERTIES v Extrusion at 250 F. Compound" Polymer of ML-4 at Appear- Feed Dis- Run No. 212 F. In./mln. G./mln. ance a rating persion 1 (control) 68 43 70 11 2 Poor. 2 75 67 112 8 Good.

Range 3-12, 12 best. b Range 0-10, best.

PHYSICAL PROPERTIES Comp.- 30 0 Elonga- Tear at Resilr r Polymer 0! se modulus, Tensile, tion, 200 11, AT lence, Hardnessp Run No. 1 percent p.s. p.s.i. percent lbJln. 1. percent Shore A.

H v 80 min. cure at 307 F.

1 (COntX'OlL-.. 8.7 1,560 3,380 510 110 '50 6s 61 2 8. 6 1, 470 3, 530 540 120 59 67 61 Oven aged 24 hour'sat 212 F. 1 (control) 2,200 2,800 360 s2 72 64 v 2 2, 080 2, 770 370 54 72 65 MASTM D 1646-61:

5 ASTM D 1646-62T.

ASTM D 624-154 Die A-Crescent. .ASIM D 1646-62. AS'IM D 1646-59. I ASTM D 1706-61.

As will-be evident to those skilled in the art, various modifications of this invention can be made or followed, in, light of the disclosure and discussion herein'set forth without departing from the scope or the spirit thereof.

-I claim: 1 1. In a process for preparing conjugated diene polymers with an organoalkali-metal polymerization initiator, the improvement comprising adding to the polymerization reaction mixture, prior to deactivation of said organoalkalimetal initiator, an ally] amine represented by wherein R is a hydrocarbon radical containing from about 1 to carbon atoms and is selected from aliphatic, cycloaliphatic, or aromatic radicals, m is 1, 2 or 3; and N is the valence of n minus m; wherein said allyl amine is added in an amount to provide from about 0.1 to 5 millimoles of said allyl amine per 100 grams of monomers employed in preparing said conjugated diene polymers, and wherein said conjugated diene polymers are conjugated diene homopolymers of copolymers of different conjugated dienes with each other, or copolymers of .conjugated dienes with monovinyl substituted aromatic hydroc'arbons.

rner are provided, and wherein from about 0.1"" hours are allowed to elapse after said allyl" amine is added and before said deactivation of said organoalkali-me't'al initiator. v v, 5. The process of claim 4 wherein from about 0.5 to 2 hours are allowed to elapse after said"allyl amine is added and before said deactivation of said organoalkalimetal initiator and wherein said conjugateddiene'polymer is a homopolymer of butadiene or a 'copolymer ofbuta diene/styren'e. r

6. .The process of claim 1 wherein said allylam'ine' is triallylamine, said 'organoalkali'-metalinitiator is n-butyllithium, and said conjugateddienepolymer is ar -homo: polymervof butadiene or a butadiene/styrene copolymer.

7. The process according to claim l wherein'said 0. 1- ganoalkali-metal initiator is a hydrocarbyllithium compound, wherein the polymerization reaction is condycted at a temperature within the rangespf about,I,30 to: 150 C. in the presence of a hydrocarbon diluent at a pressure 7 sufiicient to maintain themonomeric materials essentially q s i h se- 8. The polymeric. productl producedfjaccording to the processofclaim'l. k w Ref eren c Cited 2. The process of claim 1 wherein said allyl amine is 0 added'at thecommencement of the polymerization reac- 1 UN B E T tion in an amount to provide from about0;25*to 1 milli- 2,008, 91 7/ 1935 Ebert et al. 260:9,4.2 mole of said allyl compoundper grams of monomer. 3,280,084 04 9 6 i 1i k e -a F831 3. The process of claim 1 wherein said allyl amine is ,3 141967 rZe in --,@260%94.-2 added during the polymerization reaction in an amount 40 2 ,9 511 26 ,:4. ,7 to provide from about 0.25 to 1 millimole ofsaid-allyl 3, 69 011 70. Trepkaet a1}. 260 124 2 amineper IOOgramsofmonomer. f

. 4. The process of claim 1 wherein saidallyl amine is JAMES Exami 1; added to the polymerization reaction after the polymers ization has essentially completed, wherein from about 0.25 0 C1.

to 1 millimole of saidallyl amine per 100 grams of mono- UNITED sums PATENT OFFICE 185% 15C CERTIFICATE OF CORRECTION Patent No, ,658,776 Floyd E. Naylor Dated April 25, 1972 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, Column 7, line ho, at the end of the line, "N" should be n Claim 1, Colunn 7, line +1, after "of" and. before "minus",

"n" should be N Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER JR. ROBERT GOTTSC Attesting Officer HALK Commissioner of Patents 

